| Opulent Glow Aesthetics Ltd | Other services | 2024 |
| Opuluxe Beauty Ltd | Wholesale & retail | 2021 |
| Oraclia Ltd | Information & communication | 2026 |
| Oran Security Services Ltd Limited | Administrative & support | 2014 |
| Oraner Limited | Real estate | 2025 |
| Orange Event Organisation Ltd | Hospitality | 2024 |
| Orazio Caffe Napoli Ltd | Wholesale & retail | 2025 |
| Orazio Icecream Ltd | Hospitality | 2025 |
| Orazio Whippy Ltd | Hospitality | 2024 |
| Orchid Products UK Ltd | Wholesale & retail | 2023 |
| Orderbid LP | | 2015 |
| Ordnance Cars Limited | Other services | 2015 |
| Ordnance Market Ltd | Wholesale & retail | 2018 |
| Ordnance MOT Centre Ltd | Wholesale & retail | 2025 |
| Orea Trading Ltd | Hospitality | 2025 |
| Oreke of London Ltd | Other services | 2018 |
| Organic HUP Ltd | Wholesale & retail | 2023 |
| Orhan Hairdressing Ltd | Other services | 2019 |
| ORI Entertainments Ltd | Other services | 2024 |
| Oriental Hong Kong Ltd | Professional & scientific | 1998 |
| Origin Consulting Services Limited | Information & communication | 2017 |
| Originalo Ltd | Wholesale & retail | 2025 |
| Originworkz Limited | Wholesale & retail | 2025 |
| Orinthia Academy Ltd | Public administration | 2023 |
| Oro-Hair Limited | Other services | 2025 |
| ORR Interior Design Ltd | Professional & scientific | 2019 |
| ORT Bookkeeping Ltd | Professional & scientific | 2021 |
| OS Builders Merchants Ltd | Wholesale & retail | 2022 |
| OS Car Rental Limited | Administrative & support | 2018 |
| Osawe's Childminding Service Ltd | Health & social care | 2025 |
| Oscar Meat Suppliers Ltd | Wholesale & retail | 2025 |
| OSE UK OIL Services & Energy Ltd | Mining & quarrying | 2024 |
| Oshan Studio Ltd | Information & communication | 2024 |
| OSL Plastering Ltd | Construction | 2023 |
| OSO Designs Ltd | Administrative & support | 2018 |
| OSP Decorators Limited | Construction | 2002 |
| OSP Residential Ltd | Construction | 2024 |
| OT Yourself Community Interest Company | Education | 2025 |
| OTB Hair and Beauty Supplies Limited | Wholesale & retail | 2020 |
| Otco Ltd | Wholesale & retail | 2012 |
| Ottoman Data Limited | Extraterritorial | 2025 |
| Ottomans Holdings Ltd | Other services | 2024 |
| OU Properties (Enfield) Limited | Real estate | 2024 |
| Ouati Limited | Construction | 2025 |
| Outsane Ltd | Information & communication | 2023 |
| Outset Care Services Ltd | Hospitality | 2017 |
| Outset Fostering Agency Ltd | Health & social care | 2019 |
| Ouze Global Services Ltd | Information & communication | 2016 |
| OVA Holding Property Ltd | Real estate | 2026 |
| Overall Properties Ltd | Financial services | 2020 |
| Overseas Cotton Ltd | Wholesale & retail | 2018 |
| OWL Business Support Limited | Administrative & support | 2023 |
| OWL Concierge LP | | 2018 |
| Ownlaw Ltd | Other services | 2020 |
| OYE OYE Company Limited | Public administration | 2022 |
| Oyedun Property Management Limited | Real estate | 2018 |
| Oyku Ltd | Other services | 2020 |
| Oytan Consultancy Services Ltd | Hospitality | 2021 |
| Oyuga C Limited | Extraterritorial | 2025 |
| OZ Car Sales Ltd | Wholesale & retail | 2022 |
| OZ Enterprises Ltd | Wholesale & retail | 2025 |
| OZ Estates Ltd | Real estate | 2026 |
| OZ Hereford Ltd | Real estate | 2023 |
| OZ Lezzet Business Consultancy Limited | Real estate | 2025 |
| OZ LUX Limited | Real estate | 2024 |
| OZ MOT Centre Ltd | Wholesale & retail | 2016 |
| OZ Naimoglu Ltd | Hospitality | 2026 |
| OZ Newbury Ltd | Financial services | 2022 |
| OZ Organisations Ltd | Hospitality | 2019 |
| OZ Property Investment Ltd | Real estate | 2024 |
| OZ TUT Jewellery and Watches Ltd | Wholesale & retail | 2023 |
| OZA Foods UK Ltd | Wholesale & retail | 2023 |
| Ozakuk Ltd | Wholesale & retail | 2025 |
| Ozan Osman Properties Limited | Real estate | 2016 |
| Ozcan Accountants Ltd | Professional & scientific | 2019 |
| Ozcan ADV & Co Ltd | Professional & scientific | 2025 |
| Ozdemir Global Ltd | Wholesale & retail | 2025 |
| Ozen Services Ltd | Information & communication | 2022 |
| Ozgul Accounts Ltd | Professional & scientific | 2011 |
| Ozgul Security Systems Ltd | Other services | 2019 |
| Ozgur Barbers Ltd | Other services | 2022 |
| Ozgur EN3 Ltd | Wholesale & retail | 2022 |
| Ozhim Edgers UK Ltd | Wholesale & retail | 2014 |
| Ozlem Bilgen Ltd | Other services | 2023 |
| Ozmenb Ltd | Wholesale & retail | 2026 |
| Ozmert Properties Ltd | Real estate | 2024 |
| Oznails Limited | Other services | 2020 |
| Ozoak Leather Limited | Wholesale & retail | 2025 |
| Ozoglu Properties Ltd | Real estate | 2024 |
| Ozpark Property Ltd | Real estate | 2024 |
| Ozturk Ltd | Transport & logistics | 2021 |
| Ozuo Healthcare Limited | Health & social care | 2021 |
| OZY Construction Limited | Construction | 2025 |
| Ozzie Catering Limited | Hospitality | 2018 |
| Ozzy's Fresh Cuts Ltd | Other services | 2025 |
| P & P Dyer Limited | Professional & scientific | 1973 |
| P & T Care Solutions Ltd | Health & social care | 2022 |
| P and L Property Services 1 Ltd | Real estate | 2016 |
| P and L Property Services Ltd | Real estate | 2016 |
| P G Herbert Limited | Information & communication | 2014 |